The verifier caller pins a customer assurance root out of band. A root carried only inside an Evidence Packet cannot authorize itself. The root certifies distinct server_attestor, gateway_runtime, and outcome_probe keys with tenant, project, environment, role, and validity scope.
Compare the root fingerprint through a second channel before accepting packets. Keep the root private key offline or in customer-controlled KMS/HSM custody for a real pilot. The reference kit stores it in a mode-0600 local file for sandbox-only rotation rehearsals; this is not production custody.
Revocation journals are signed, sequenced, hash-linked, and checked against the pinned root. Non-retroactive revocation preserves evidence signed before the effective time. Retroactive revocation invalidates historical use and must be treated as an exceptional administrative assertion.